Sigma's own "standard zoom" lens with a close 3:1 zoom range offers you the travel companion or walk around lens to capture kids playing, family events, or casual portraits. The lens features three aspherical glass elements to correct distortion, two SLD elements for optimum color correction and sharpness, and Super Multi-layer coating to minimize flare and ghosting. Designated HSH, hypersonic motor, produces quiet, fast autofocusing. Sigma 18-50mm f/2.8-4.5 also offer internal focusing system to prevent the front lens from rotating when photographing. Combined features coupled with Sony APS-C senor camera delivers high image quality across the full zoom range.